Saw-tooth wave generator



Dec. 17, 1940. GElGER 2,225,300

SAW-TOOTH GENERATOR Filed June 9., 1958 /n auf "9 INVENTOR v r MAX GE65/2 ATTORNEYS Patented Dec. 17, 1940 7 2,225,300 sAW-Too'rn WAVEGENERATOR Max Geiger, Berlin, Germany, assignor to TelefunkenGesellschaft fiir Drahtlose Telegraphic. m. b. 1-1., Berlin, Germany, acorporation of Germany Application June 9,1938, Serial-No. 212,723 InGermany February 20; 1937 8 Claims.

The invention is concernedwith I circuit organizations wherein, withaviewto producing a-linear rise of current in a choke-coil, asource ofpotential supply is applied to the choke-coil and is disconnected. againtherefrom after completion or termination of the rise of the current.Circuit arrangements-which operatein accordance with this principle areknown in the art of causing magnetic deflection by magnetic forcesacting on the cathode-ray pencil in television tubes. However, circuitschemes ofthis kind as heretofore known have the disadvantagethat therise of the current proceeds in accordance with a straightlinelaw onlyinitially, that is, in the early phase of the rise, and even then onlyunder the condition that the potential is constant and. stable, and,further, that the inner resistance of the voltage source is negligiblylow, and that the resistance of the switch break is also constant.

in practice with suficient accuracy, and as, moreover, the linearinitial portion of the currentrise curve is not always adequate,- meansand, ways are suggested in the present invention which will so changethe voltage actingat the coil v as a functionofthe coil current that thevoltage. at the coil will decrease in the presence of arapid rise of thecoil current, and will increase for a low rise of the said current.v

My invention will best be understood by reference to the figures inwhich Fig. 1 shows one embodiment thereof,

' Fig. 2 shows a second embodiment thereof,

Fig. 3'shows a modification of the arrangement of Fig. 2, and

Figs. 4 and 5 show still further embodiments of my invention.

The exemplified embodiment shown in Fig. 1 comprises a screen-grid tubeI 0, the deflector coil II of a cathode-ray tube, a rectifier I2, aresistance I3 and a source of plate potential supply I4. If theresistance I3 is assumed to be replaced by a source of D. C. voltagesupply whose negative pole is united with the anode of the rectifier I2,then the circuit arrangement comprising the elements designatedby,III-J4 is known in the art. An auxiliary coil I5;- a further tube I6con-jointly with the resistance I3 accordingto the invention arearranged in the. known circuit organization to the end of causing asteady change of the voltage acting at the vcoil in such a way that therise of the current will be caused to obey a straight-line law.

In this figure there is shown a vacuum tube II] having anode, cathode,control and screen elec- Since these assumptions are not alwaysfulfilledductance coil I5 is energized through alead which isrconnected withplate supply battery I4. 1

The anode ofthe tube It is connected directly to the anode of. the tubeI2 and the cathode of tube I6 is grounded.

In order to explainmore fully the operation of the circuit organization.shown inFig- 1, the circuit elements I5,- I6, as well as the resistanceI3sha'll first be. disregarded, and the supposition shall be made thatin lieu ofthe resistance, I3 a source of D. C. voltage supply isconnected in a way as above stated inseries with the rectifier I2. Thiscircuit organization, as already pointed out,

is known in the art" and the same will then operatev insucha way thatfor the production of the linear current rise the rectifier I2 isrendered conductive for current. This is eiiected for a period of timefor which the current flowing in the coil II has a direction whichconventionally flows from the positiveterminal of the battery I4i'to*theanode of the tube ID as a resultof the fact that at the control grid .oftube I0 isimpressed a potential which will allow a flow of currentthrough this tube. The plate current flows throughthe rectifier I2 andat the-coil thus acts the voltage furnished from the source of D. 'C.voltage supply supposedto take the place of the resistance I 3. If bysuitable blocking voltage at the control grid of tube Ill the flow ofcurrent across this tube and the rectifier I2 is out off, the cell willexperience a half oscillation'in'such a way that the voltage actingthereon is inversed so that it thus-resumes the polarity which it hadduring the linear rise of current, while incidentally surpassing thevalue of the voltage of the sourceof D. C. potentialsupply. Hence, thevoltage acting at the coilis able to overcome the voltage which is to beassumed instead of the resistance I3 and to thus re-open or unblock therectifier I2. Without the opening of tube IIlbeing required, the sourceof D. C. potential supply will thereafter be connected again through therectifier I2 with the coil'so that-,-,in

spite of the reversal of the sense of the current flow in the coil, thedifferential quotient of the coil current will again possess the samesize and conventionally in such a direction as to fiow from the positiveterminal of the battery I4 to the anode of tube It. However, before thecoil current passes through the zero value a current must be initiatedthrough the rectifier I2 by the opening of tube Ii since zero coilcurrent could otherwise not be exceeded. Now, the circuit elements I3,I5 and I6 operate in such a way that during the linear rise of thecurrent, at the auxiliary coil I5, there will arise a voltage of suchpolarity as to render the terminal thereof connected to tube Itnegative, and the terminal thereof joined to battery I4 positive, andthis voltage acts as the regulator voltage for tube I6. In the gridcircuit of the said tube I6 there thus acts a positive grid potential(namely, the voltage between the left-hand end of the plate potentialsource of supply I4 and its tap) in series with a negative grid biasingvoltage, the latter being furnished from the auxiliary coil I5 in amanner as hereinbefore described. The size of the positive grid voltagemust exceed that of the negative voltage so that, for a constant size ofthe negative grid voltage, a finite plate current is able to flow acrossthe tube I6 by way of the resistance I3. This plate current results in afall of potential across resistance I3 whereby the terminal thereofconnected to the anode of tube I2 is rendered negative and the terminalconnected to battery I4 is positive and which at the same timerepresents the voltage acting at coil I I being constant in the knowninstance. If, then,'the current in the coil II starts to rise morerapidly, the negative grid voltage experiences an increase, and the dropof potential across the resistance I3 as a result diminishes. However,this does not mean anything else but that the voltage decreases acrossthe coil II and this, in turn, implies that also the slope or steepnessof the current rise in this coil must diminish. If, on the contrary, thesteepness of the current rise in the coil II decreases, this implies areduction of the negative grid potential; hence, the positive gridpotential predominates, and this results in an increase of the platecurrent of tube I6 and thus also of the drop of voltage acrossresistance I3. As a result there occurs thus a growth of potential atthe coil II, and this will also speed or accelerate the rate of currentrise. It will thus be seen that no matter whether there is a tendency onthe part of the coil current to either rise faster or less fast, therewill instantaneously be caused a compensation of such tendency becauseof the fact that the voltage drop across resistance I3 is a function ofthe current rise through the coil.

The exemplified embodiment shown in Fig, 2 difiers from that in Fig. 1in as far as the auxiliary coil I5 is included in the control-gridcircuit of a tube I'I provided in lieu of the rectifier I2; if desired,the said control-grid circuit in addition may be supplied with anegative biasing potential furnished from the RC mesh. In lieu of theresistance I3, Fig. 1 there is provided another RC mesh I9 as known in acircuit arrangement Fig. 2, though without the coil I5, the RC mesh I8and with a rectifier instead of tube II.

In this figure the screen grid tube III has an inductance II connectedserially with the anode thereof and a plate supply battery I4 has thepositive terminal thereof connected to one terminal of the inductance II, and the negative ter minal thereof connected to the cathode, thelatter being grounded. There is provided a second thermionic tube I!having anode, cathode and control electrodes, the cathode of the tubebeing connected to the common terminal of the anode of tube III and theinductance II through a time constant circuit I8. A common terminal ofthe time constant circuit I8 is connected to the control grid of tube IIthrough an inductance I5 which is positioned immediately adjacent theinductance II and is coupled therewith. The anode of tube I1 isconnected to the common terminal of inductance II and plate supplybattery I4 through a time constant circuit I9.

The circuit scheme Fig. 2 operates in this manner that, in the presenceof a steep rise of the current in the coil II the grid potential of tubeI1 is reduced, which, in turn, means an increase in internal resistance,so that a greater portion of the practically constant potential existentat the RC mesh I9 drops at the tube II. But if the rise of the currentin the coil I2 is too flat or slow, this results in a decrease of thevoltage furnished from the auxiliary coil I5; hence, the grid potentialof the tube I'I rises, its internal resistance diminishes, and at thecoil II occurs an increase in the potential which, in turn, will causethe current in this coil to rise again With the desired slope.

Instead of the two distinct RC meshes I8 and I9, it would also bepossible to use a joint RC mesh 20 as shown in Fig. 3 from which, byproviding a suitable tap for the resistance such negative grid biasingvoltage for tube as may be desired can be tapped.

The showing of Fig. 3 is essentially the'same as that of Fig. 2 with theexception that the time constant circuit H) of Fig. 2 which is connectedto the anode of tube I1 and the common terminal of inductance II andplate supply battery I4 has been omitted.

In the embodiment shown in Fig. 4 there is also provided a tube IT inthe sense of Figs. 2 and 3, and an RC mesh I9 in the sense of Fig. 2. Inlieu of the auxiliary coil I5 there is here used a tetrode as well as aresistance 22, the series arrangement of these two element beingconnected in parallel relation to the coil I I.

In this figure a screen grid tube II] has an inductance II connecteddirectly to the anode of tube Ill and serially with plate supply batteryI4, the negative terminal of which is connected to the cathode of tubeIII, the latter being grounded. A screen grid tube 2I has the spacedischarge path thereof connected serially with a resistor 22 and thisseries circuit is connected substantially in parallel with inductanceII, the anode of the tube being connected to the common terminal ofinductance II and plate supply battery I4, and the terminal of resistor22 remote from the cathode of tube 2I is connected to the commonterminal of the anode of tube I0 and inductance II. The controlelectrode of tube 2I is variably biased by plate supply battery I4, asis the screen electrode of the same tube. A thermionic tube I! havinganode, cathode and one control electrode has the space discharge paththereof connected serially with a time constant circuit I9, the latterbeing connected directly to the anode of tube 2| and the cathode thereofbeing connected directly to the common terminal of inductance I I andresistor 22. The control electrode of tube I1 is connected to the commonterminal of tube H and resistor 22.

The circuit organization shown in Fig. 4

works .in' Ithisunannerthatby suitable .choice :of

:the 1 :potential impressedv 'iupon ".the -.control :and .screen 1 gridsofttubel :21 the' operating point of ttheaplate"currenteplatervoltage"characteristic is L-placed in f the neighborhood of plate: currentsaturation. a If, then, r the. voltage at :the coil should happen to"rise, Kin. other words, if the current: through this" coil increasesiits islope 1 or steepness, this .will be': attended withziarr increase:is lessened. :But Iifg: on; itheicontrary the: voltage at coilliltdecreases, so that 'the'steepnessof current rise :decreases, thenetube =1 9 will be further 'opened' with the result. that --through'. 'a*rise- 1 of 1 voltage'across the coil :ll the rate of :current'irise isiboosted agaim: .s, W i

elf.

In the exemplified embodiment shown inFig. 5,.a tubei23 andJa resistance24 being connected in series with each other, are provided in parallelrelation to the coil H. Tube I 6 corresponds to the tube Fig. 1 bearingthe identical reference numeral, and resistance [3' corresponds to theresistance with the identical reference numeral therein provided. Thegrid circuit of tube It includes further a blocking condenser 25 and aresistance 26 which is united with a suitable biasing voltage.

The circuit arrangement of Fig. 5 is as follows: A screen grid tube IDhas the anode thereof serially connected'with an inductance H and aplate supply battery [4, the negative terminal of the latter beingconnectedto the cathode of the tube and the cathode being grounded. A-

series circuit comprising the space discharge path of a thermionic tube23, this tube having anode, cathode and one control electrode, and aresistor 24 is connected in parallel with the inductance II, the cathodeof the tubebeing con- 'nected to the common terminal of the,,anode oftube It) and the inductance H, and the terminal of resistor 24 remotefrom the anode of tube 23 being connectedto the common terminal ofinductance II and plate supply battery l4. Also connected in parallelwith the inductance H is a diode I2 and a resistor I3, the cathode ofthe diode l2 being connected to the cathode of tube 23. The bias for thecontrol grid of tube 23 is supplied from the variable tap on the batteryit connected to the control electrode thereof. A fourth tube l6 havinganode, cathode and one control electrode, has the anode thereofconnected to the common terminal of the anode "of diode l2 and theresistor l3 andhasthe cathode thereof grounded. The control electrode oftube I 6 is connected through a condenser 25 to the common terminal ofthe anode of tube 23 and the resistor 24. Connected directly to thecontrol electrode of tube I6 is a resistor 26,

the latter being grounded through an appropriate biasing means. I

If in a circuit arrangement as shown in Fig. 5, the voltage acting atthe coil undergoes a growth, this occasions a rise in the innerresistance of the tube 23 and thus also a rise of the grid potential oftube I 6. The result is that a decrease of voltage across'resistance l3happens, and this means that also the rise of current at the coil 1 Ibecomes less. If, inversely, the voltage at coil ll diminishes,thismeans an increase-of tgrid: potential of. :tube 'l'6;rises,:the;dropof potencurrent J-are raised.

. The invention-sis of .practicalvalue not only .for the. productionofsaW-tooth-shaped currents .-of:..the kind required for the magneticdeflection of "cathode-ray; pencils for .television work, but

:also forzso-called.imagezconverter tubes. fThese tubes comprise a.photo-icathode and. a lumines- :cent'or mosaic sscreen,=fand thephoto-cathode may ibewprojected"or-:imaged by electron optic aways-andmeans .upon the said luminescent screen :3 vlthe inner resistance of.tube123 :hence, the control A itial'z.acrossuresistance' l 3 and: thus.the rise i of .coil J or mosaic screen, andthey maytbe operated .in'

:such amanner, as. previously suggested .inlthe ;art, that-of an object:mo'ved ataa uniform rate ofaspeeda migrating or shifting photo-optic:image is produced 'upon' the. photo-cathode, while -by suitabledeflection. of the pencil ofzelectron raysuaz'static luminescentorcharge pattern or image is produced upon the mosaic. screen.

Moreover; theoinvention may be Lutilized in practice "alsoindependently'of whether after completion. of the linear rise ofcurrent. the coil H undergoes a free half-cycle alone or in conjunctionwith a capacity connected in parallel with it or whether, say, bymeansof a counteracting voltage applied to the coil a still faster change ofthe current is obtained than that which would correspond to the naturalperiod of the coil or to the resonant circuit formed by the coil and theparalleled condenser.

What I claim is:

1. Saw-tooth wave generator means for storing electromagnetic energy,means for storing energy in said storage means, and means for applying acompensating voltage to said storage means, said. compensating meansbeing adapted to generate a compensating voltage in accordance with therate of change of current in the electromagnetic storage means.

2. An electric generator comprising means for storing electromagneticenergy, means for storing energy in said storage means, and means forapplying a compensating voltage to said storage comprising means, saidcompensating means being adapted of the energy in said storage means,and means,

for impressing saidcorrective potential on to a current carryingelectrode of said unilateral conductor.

4. A saw-tooth wave generator comprising means for storingelectromagnetic energy, means for storing energy in said storage means,a diode, a resistor connected in the anode-cathode circuit a circuitwhich is connected in parallelwith said energy storage means, athermionic vacuum tube having anode, cathode, and at least one controlelectrode, means for connecting the anode.

of said thermionic tube to said resistive means, and means forimpressing a portion of the energy in said electromagnetic" storagemeans onto a control electrode of said thermionic tube.

5. A saw-tooth wave generator comprising electromagnetic energy storagemeans,means for storing energy in said storage means, a thermof saiddiode, said diode and said resistor forming ionic tube having anode,cathode and at least one control electrode, at least one time constantcircuit connected in the anode-cathode circuit of said thermionic tube,said anode-cathode circuit and said time constant circuit comprising aseries circuit which is connected substantially in parallel with saidenergy storage means, and means for impressing a portion of the energyof said electromagnetic storage means onto a control electrode of saidthermionic tube.

6. Apparatus in accordance with claim 5 wherein a second time constantcircuit is connected in the control electrode-cathode circuit of saidthermionic tube.

'7. A saw-tooth wave generator comprising electromagnetic energy storagemeans, a first thermionic vacuum tube having anode and cathodeelectrodes, a resistor connected in the anode-cathode circuit of saidtube, said anodecathode circuit and said resistor comprising a seriescircuit which is connected substantially in parallel with saidelectromagnetic energy storage means, a diode, a second resistive memberconnected in the anode-cathode circuit of said diode, said anode-cathodecircuit of said diode and said second resistance forming a seriescircuit which is connected substantially in parallel with saidelectromagnetic energy storage means, a second thermionic vacuum tubehaving anode, cathode and at least one control electrode, means forimpressing the anode current of said second thermionic vacuum tube ontoat least a portion of said second resistance, and means for impressingvariations in the anode-current of said first vacuum tube onto thecontrol electrode of said second thermionic vacuum tube.

8. The method of linearly storing and discharging electromagnetic energywhich comprises the steps of storing electromagnetic energy andsimultaneously developing a potential bearing a definite relationship tothe rate of change of storing of said energy and correcting forirregularities in the linearity of the storing and discharging of energyin accordance with the value of the potential bearing the definiterelationship to the rate of change of storing. said electromagneticenergy.

' .MAX GEIGER.

